1. Field of the Invention
The present invention relates to a thermo-sensitive resistor used, for example, for detecting an amount of fluid flow in an itnernal combustion engine by utilizing a thermal dependence of the resistance thereof.
2. Related Art Statement
Heretofore, an adjustment of resistance of such a thermo-sensitive resistor having a thin-film heating resistor formed by a sputtering method or an evaporation method has been performed by a laser trimming method as disclosed, for example, in Japanese Patent Laid-Open Publication No. 175,580/84.
However, if the resistance adjustment of a thin-film heating resistor having thickness variations is perfromed by the conventional laser trimming method, the trimming operation must be stopped when the resistance reaches a predetermined value. That is to say when adjusting the resistance of several thin-film resistors having the same planar dimensions but varying thicknesses, it is necessary to vary the trimming area of each resistor one at a time in order to adjust the resistance of each resistor to the same value. Accordingly, a drawback occurs in that the area for heating each resistor (i.e., the planar area of each resistor) is varied from resistor to resistor when the conventional laser trimming method is employed.
Moreover, as mentioned above, since the area for heating is varied between thermo-sensitive resistors, a temperature distribution of the thermo-sensitive resistor is varied from resistor to resistor correspondingly and a thermal diffusionability is also varied. Therefore, when an amount or speed of a fluid flow is to be detected by using the thermo-sensitive resistor mentioned above, characteristics, such as detection accuracy and response, of the detector utilizing the thermo-sensitive resistor are varied.